During peak shopping seasons many vendors struggle to keep track of stock. In an effort to improve stock control, many vendors have turned to the use of radio frequency identification (RFID) tags. There are five general types of RFID tags. They are inductively coupled, capacitively coupled, active, semi-active, and passive RFID tags. All five types of RFID tags operate using similar steps. Data is stored within an RFID tag's microchip and the tag is attached to an item to be tracked. The tag's antenna receives electromagnetic energy from an RFID detector's antenna. Using power from an internal battery or power harvested from the detector's electromagnetic field, the RFID tag sends radio waves back to the detector. The detector picks up the radio waves and interprets the frequencies as meaningful data.
In general, RFID tags attached to items being purchased are deactivated during checkout. However, this does not always occur, e.g., when there is a malfunction of the RFID tag de-activator or when an RFID tag is not de-activated by a cashier. When an active RFID tag enters into range of an RFID detector, the detector indicates the presence of the active RFID tag, often through the use of a siren or other alarm. This can lead to general confusion for customers as there may be numerous individuals within range of the RFID detector and all of whom may have multiple purchases.